Gas non-return valves (check valves) protect systems, outlet points and pipelines against unwanted and potentially hazardous gas mixtures.

For applications in the high-pressure range, the German manufacturer WITT provides two models, one with a maximum operating overpressure of 300-bar (4350psi), in its current 600H and 800-ES series.

The 600H model with brass housing can be used for combustible gases, oxygen and non-flammable gases. It has a particularly sensitive mechanism and reacts from about 250-mbar (3.6psi) opening pressure. Its maximum operating overpressure is 40-bar (580 psi). With compact dimensions and position-independent installation, a broad spectrum of applications is possible. The ambient temperature may be 70°C (158°F) in the 600 model, and several connection sizes with G threads are available, as well as a stainless steel version (600H-ES).

The 800-ES model can withstand pressures as high as 300-bar (4350psi) when used with combustible gases. Even with oxygen, 240-bar (3480psi) is possible. This stainless steel model is suitable for a large number of technical and corrosive gases. It can be installed independently of environmental constraints, which means the ambient temperature at the installation site can be up to 150°C (302°F) with fuel gases and 60°C (140°F) with oxygen. According to WITT, the spring-loaded valve system with elastomer seal ensures maximum leak-tightness. It opens at 2-bar (29psi) and above.

Another advantage of the 800-ES is its compact design, which enables installation when space is restricted. Weighing 730 grams (1.6 lbs), the component measures less than 70 mm (2.75 inches) in length and only 18 mm (0.7 inches) in diameter. The 800-ES has a standard 1/4-inch NPT thread.

Gas non-return valves made by WITT are tested individually for correct functioning before delivery. Dirt filters in the inlet ensure long service lives.

Typical applications for gas non-return valves include all systems, pressure control stations and pipes conveying inflammable gases, anywhere a reverse gas flow could form unwanted and dangerous mixtures. In the worst case scenario, such a mixture could result in an explosion. Gas non-return valves prevent this by stopping a creeping or sudden gas flow in an unwanted direction.